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[Qemu-devel] [PATCH v2] net: cadence_gem: clear RX control descriptor

From: Ramon Fried
Subject: [Qemu-devel] [PATCH v2] net: cadence_gem: clear RX control descriptor
Date: Tue, 16 Jul 2019 13:59:51 +0300

The RX ring descriptors control field is used for setting
SOF and EOF (start of frame and end of frame).
The SOF and EOF weren't cleared from the previous descriptors,
causing inconsistencies in ring buffer.
Fix that by clearing the control field of every descriptors we're

Signed-off-by: Ramon Fried <address@hidden>
Reviewed-by: Philippe Mathieu-Daudé <address@hidden>

  * change function name to rx_desc_clear_control as proposed by
    Jason Wang
  * Move the function call above the comment, as proposed by
    Philippe Mathieu-Daudé

 hw/net/cadence_gem.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/hw/net/cadence_gem.c b/hw/net/cadence_gem.c
index ecee22525c..cca3ce7f56 100644
--- a/hw/net/cadence_gem.c
+++ b/hw/net/cadence_gem.c
@@ -406,6 +406,11 @@ static inline void rx_desc_set_sof(uint32_t *desc)
     desc[1] |= DESC_1_RX_SOF;
+static inline void rx_desc_clear_control(uint32_t *desc)
+    desc[1]  = 0;
 static inline void rx_desc_set_eof(uint32_t *desc)
     desc[1] |= DESC_1_RX_EOF;
@@ -993,6 +998,8 @@ static ssize_t gem_receive(NetClientState *nc, const 
uint8_t *buf, size_t size)
         rxbuf_ptr += MIN(bytes_to_copy, rxbufsize);
         bytes_to_copy -= MIN(bytes_to_copy, rxbufsize);
+        rx_desc_clear_control(s->rx_desc[q]);
         /* Update the descriptor.  */
         if (first_desc) {

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